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Wednesday, March 28, 2012

One of the more common early spring wasps here in the Front Range of Colorado is an ichneumon wasp in the genus Spilichneumon. According to the Database of Hymenoptera in America north of Mexico there are at least four species in the state, so perhaps I am seeing more than one.

These wasps are active and skittish enough that they defy my ability to get really crisp images of live specimens, but I have found two deceased individuals on bike trails here in Colorado Springs. Plus, my fiancée found one at the Cheyenne Mountain Zoo. This specimen is shown below.

These wasps overwinter as adults, inside rotten logs and other protected situations, so they are among the first wasps one is likely to encounter by winter’s end.

Members of the genus Spilichneumon are not well-known, at least in the western U.S. The global range of the genus is the northern hemisphere (termed “holarctic”), and Oriental. Here in North America, most species are found in the extreme northern U.S., Canada, and Alaska, and along major mountain ranges as far south as Arizona.

This is yet another wasp you can count among your friends. Spilichneumon is an internal parasite of noctuid moth caterpillars. The female wasp finds a caterpillar and injects a single egg into it. Her larval offspring then feeds inside the caterpillar, allowing the host to eventually graduate to its pupal stage. The wasp larva pupates inside the host and emerges from the host chrysalis as an adult wasp.

I wonder if Spilichneumon competes with the cutworm-hunting sphecid wasps in the genus Podalonia? Both go after the same prey, at least in part, but Podalonia appears to be far more abundant here than the ichneumons. My observations may be biased, however, since I am usually out at the warmest part of the day, when Podalonia is most active. Spilichneumon, and other genera in the subfamily Ichneumoninae, tend to shun extreme heat and direct sunlight.

Look for this genus where you live. See Bugguide for better images. Look on the forest floor in open woodlands, as the wasps tend to seek their prey among leaf litter.

Wednesday, March 21, 2012

Last “Wasp Wednesday” I featured some very early emerging ”Winter Wasps” that I have recently encountered during the unseasonably warm weather here in Colorado Springs. Today I’ll focus on one of those: Liris. They are among the first solitary wasps of the family Crabronidae that you are likely to see in the spring. That is because the females overwinter as adults.

Beyond the early appearance of these wasps, I find other characters at least semi-reliable for distinguishing Liris from other members of the tribe Larrini. The antennae, frequently held parallel and straight out from the head, are proportionately longer in Liris than in Tachytes and Tachysphex. Tachysphex is usually considerably smaller than Liris, often with the abdomen entirely red, or red in part, and terminating in a very pointed pygidium. Tachytes frequently has bright green eyes, and is generally stockier in appearance than Liris. Tachytes rarely sit still for more than a millisecond (or so it seems), whereas Liris seems to move at least slightly more slowly.

Liris is a large genus with most of its diversity in the tropics. Over 260 species are known worldwide, but that is likely to increase substantially since the genus is poorly known in the New World tropics and in Asia. Krombein and Gingras revised the North American species (including Mexico) in 1984, but only two species, L. argentatus and L. beata are consistently found north of the extreme southern U.S. Species identification hinges on obscure characters like the male genitalia, female pygidium (a triangular plate on the last dorsal abdominal segment), and the size and shape of the sensory areas on the antennal segments. When the reference includes electron microscopy images, you can forget about making species identifications in the field.

illustration by Judy Jay (Bohart & Menke, 1976)

Still, I am willing to bet that the species I am observing here in Colorado Springs is Liris argentatus. It is by far the most abundant of all North American species in the genus, and found from southern Ontario and Massachusetts west to southeast Washington state, south to Panama. It is also one of the most studied species, so there is a wealth of information on its biology and behavior.

Females of L. argentatus vary from 9.5-15.4 mm in body length. Males are 6.4-10.7 mm. They are thus medium-sized insects. Both genders are black, but covered in fine, short, reflective hairs that give them a decidedly silvery appearance in bright sunlight.

My observations over the last two weeks indicate that one of the first priorities of newly-emerged females is to find water. Indeed, I have seen at least three individuals, on two separate occasions, taking water from damp soil in otherwise dry arroyos in Red Rock Canyon Open Space and Garden of the Gods, right around noon or one o’clock PM.

Both sexes will also seek fuel in the form of honeydew secreted by scale insects, and nectar from flowers as diverse as thistle, sunflower, wild carrot, and goldenrod.

The females next prepare nest burrows. Lacking a strong rake of tarsal spines on their front legs, females of L. argentatus may clean out pre-existing tunnels and cavities to use as nests. There are still plenty of records of this wasp digging its own burrows, terminating in one to three underground cells (one recorded nest had a cluster of ten cells). The nest varies from 10-14 centimeters in depth and is left open while the wasp begins its search for prey.

Crickets in the family Gryllidae are the host animals sought by these wasps. Both adult crickets and nymphs are taken. The prey is paralyzed by the wasp’s sting, facilitating easier transport of what is truly a bulky animal. The wasp grasps the prey by the base of its antennae and lugs it overland on most occasions. One to four (sometimes more) crickets are placed in each cell at the bottom of the burrow, an egg laid on the last victim. Oddly, the crickets are not completely paralyzed, recovering the ability to walk weakly, or even jump in some cases.

Once a nest is filled, the wasp fills the tunnel loosely with a combination of soil particles and fragments of dry vegetation, small pebbles, and other debris. She hides the entrance by kicking sand or soil over it, then leaves to repeat the whole scenario again.

Nests constructed in spring are remarkably devoid of parasites, but then the “satellite flies” that plague so many solitary wasps have not yet emerged themselves. Even velvet ants are only just beginning to stir. Nests made in the summer do suffer parasitism.

Those late-season wasps that do make it will mate before winter. Only the females live through the cold months, evidently inside burrows they dig for the purpose of hibernation.

Those of you in the U.S. and Canada can probably find these wasps in your own area very soon, if not right now. Please feel free to share your comments and observations here. There is still so much to learn about even the most common of insects, and you could be the one to make a significant contribution to our collective body of knowledge.

Wednesday, March 14, 2012

I am taking advantage of the unseasonably warm weather this week (71°F today, predicted to stay that way or go higher through Saturday) to explore various wild areas around Colorado Springs. It means I won't be doing many blog entries now, but will have fodder for later entries. Also, I'm running low on wasps I have images of!

Do consider visiting my Flickr photostream this week, as I'll be posting new images there. Thank you and have a great rest of the week!

Sunday, March 11, 2012

It really isn’t quite spring here on the Front Range, but neither is it winter, at least not lately. The high temperature for Tuesday, March 6 was 69°F, albeit windy. Walking down the Homestead Trail in Colorado Springs at midday I was amazed by how many spiders were out and about as well.

A surprising number of spider species overwinter as adults or immature, forsaking the cozy shelter of an egg sac in which to endure the harsh, cold extremes. Among them are running crab spiders (family Philodromidae, image below), crab spiders (Thomisidae), wolf spiders (Lycosidae), and jumping spiders (Salticidae).

Most of these arachnids are ground-dwellers, so presumably they ensconce themselves in debris such as leaf litter, or tuck themselves into the base of grass tussocks. Even a blanket of snow helps insulate spiders from colder air temperatures and chilly winds.

Spider bodies also contain glycerol, a chemical compound that helps reduce the freezing point of their blood, by about one degree Centigrade (Celsius). Certain proteins in spider blood (hemolymph) apparently reduce the freezing threat even more, up to 20°C. Spiders of temperate climates that overwinter in a passive state tend to be much more cold-hardy than those that are winter-active, like some wolf spiders in the genus Pardosa.

Spiders fall into different categories depending on their reproductive cycle. “Eurychronous” species take a long time to reach maturity, and so may overwinter as adults or immatures. “Stenochronous” spiders include those that reproduce during spring and summer (overwintering as immatures); those that mate in autumn (with the spiderlings overwintering inside the egg sac); and those spiders that are active during the winter, reproducing at that time. Lastly, “diplochronous” species have two reproductive cycles, one in the spring and one in the fall. Typically, they overwinter as adults.

The most abundant adult spiders I have found recently are running crab spiders in the genus Thanatus, family Philodromidae. Numerous specimens were basking on the concrete path of the Homestead Trail. A gust of wind caught one unfortunate specimen, sending it tumbling head over heel, heel, heel, heel, heel, heel, heel, heel.

One short stretch of trail also produced two very gravid female crab spiders in the genus Xysticus. “Gravid” means full of eggs. I’ll be looking for them next in silken retreats guarding their egg sacs. Crab spiders are typically ambush hunters, lying in wait for a potential victim to come within reach. Their extra-long first and second pair of legs means that “reach” is considerable, and spines lining the inside of their legs help insure that prey does not escape the spider’s embrace.

Wolf spiders are also on the move, and a short distance from the crab spiders I spotted a plump adult female heading for cover at the edge of the trail. Fortunately, she stopped just short momentarily, posing for a couple of pictures. My friend and colleague Mandy Howe kindly identified this as a female in the genus Alopecosa. She’ll soon have an egg sac attached to her spinnerets (the spider, not Mandy!).

I also found another wolf spider, much smaller and quicker. This is probably an immature in the genus Schizocosa, judging by its color pattern. It bears a superficial resemblance to the Thanatus in that both have stripes on the cephalothorax and a dark “cardiac” mark on the top of the abdomen. This pattern is effective camouflage among grasses and seeds, rendering the animals nearly invisible unless they move. I appreciate the concrete substrate for photography, as one easily loses track of the subject on a more natural surface.

Hiking in Red Rock Canyon Open Space on March 5, a 68°F day, yielded a pair of jumping spiders along the trail. I only managed to get the image below before the tiny arachnid hopped away. I have no idea whether it is an immature or an adult, let alone what genus it might be.

I encourage you to go spider-hunting yourself on the next nice day. It need not be that terribly warm, and I have seen spiders on the surface of the snow before. Look carefully, as some of the most abundant spiders of winter and early spring are the tiniest: dwarf spiders in the subfamily Erigoninae of Linyphiidae. Some juvenile cobweb weavers (Theridiidae) and funnel weavers (Agelenidae) can also be common.

Friday, March 9, 2012

I almost never entertain a guest blog, but I found the following post to the Entomo-l listserv (an international e-mail group of mostly professional entomologists) to be more than worthy of space here.

Dave Green is a beekeeper in rural South Carolina who is equally interested in native bees and other pollinating insects. He has been at this a long time (he goes by ”Old Drone”) and I value his observations and opinions. Here he paints a very hopeful picture of the immediate future of honeybee-dependent agriculture.

”This year's swarm season began early with a humungous swarm in mid-February - six weeks ahead of the norm. Investigation shows that none of my hives could have thrown that swarm. So it must have come from a feral hive.

It was a bushel of bees - just like the old swarms we used to see before three parasites and new diseases created hives that could only seem to build to about half the strength of the old timey hives.

My own hives are roaring strong, as well as several hundred commercial hives I looked at before they left for California's almonds last month. They are beautiful bees! It's thrilling to open a hive in late winter to see wall-to-wall bees, even spilling over the edges of the hives.

Colony Collapse Disorder? No sign of this!

We've been seeing continuous hype about the honey bees dying off; and I've been saying, "Hold off. Our beekeeping industry is dealing with this. While the possibility is scarey, it isn't happening yet.

My own observations are confirmed by reports from California, where the almond industry is now engaged in the largest managed annual pollination event in the world - where a million hives from all over the USA come to that state to ensure one of the country's most nutrition-packed and valuable crops.

An article in the Los Angeles Times tells about Paramount, the world's biggest almond grower, with 47,000 acres under cultivation.

’Almonds are our primary crop and the most critical because they bloom for a short period; it's early in the season and we must have bees to pollinate,’ said Paramount President Joe Macilvaine.

‘Lots of things can reduce almond yield — weather conditions, drought, insect infestations,’ Macilvaine said. ‘But if you don't have the bees, you never get to begin.’

Paramont uses managed bees, both Blue Orchard (solitary) bees and honey bees. ‘This season, Paramount contracted with 26 beekeepers to bring in 92,000 hives from as far as Maine, Louisiana, Florida and the Carolinas. The rental expense represents 15% of the company's total almond production cost.’

And the honey bees are looking very good this year!

‘We're looking at the best bees we've seen in five years,’ Paramount staff entomologist Gordon Wardell said. ‘The bees are better because the beekeepers are getting better at managing them.’

In the past, a mild winter could often be a problem. With more winter bloom, bees put in more flight time, eating up honey reserves. Winter flowers are pollen-rich and nectar-poor.

Toward the end of winter, the bees have often used up all the stored honey, and are living on day-to-day nectar. A spell of cold or wet weather can cause mass starvation. Sadly, it's the most powerful hives that have been vulnerable to this. In just a few days of starvation, a strong hive can become weak or even dead.

Beekeepers have become much better guardians against starvation - and indeed are much more aware of all the nutrional needs of the bees. The commercial bees I looked at have been well fed with both carbohydrates and pollen/protein since mid-winter.

But there is another side to the story.

Many times in my career, I've seen bees that looked beautiful - in the spring. A mild winter's pollen-rich flowers help them clear out all the old contaminated pollens.

But then I've watched them dwindle and turn poor as the pesticide season comes into swing. When the spraying begins - the bees start taking hits. Sometimes this is noticeable, sometimes colonies are even killed. But most of the damage is seen in weak hives that are simply struggling to survive.

So, while I rejoice at the great start to the season, I'll be watching to see if this is a trend, or the same old story I've seen so many times.

We all need to be watching. When this is seen in managed bees, what is going on with wild bees that are not being observed?

Wednesday, March 7, 2012

Perhaps I should call this entry “early spring wasps.” We have had a very mild winter here in Colorado Springs, Colorado, and it seems that spring comes earlier and earlier now, no matter where one lives. Certainly more southerly latitudes are experiencing spring right now. Still, I am amazed by the wasps I am finding on the wing already.

While out hiking an urban trail on February 29, I found female Podalonia cutworm wasps out and about in the 58°F temperature. Perhaps they were hunting for those Army Cutworm caterpillars that have also been roaming on warm days. One of the wasps I observed was digging, but I could not discern whether she was excavating a burrow for prey she already had, or was unearthing a moth larva.

A few days previous to Leap Day, Heidi had brought me a wasp that she found flying around one of the exhibits in Primate World at the Cheyenne Mountain Zoo where she works. She had already correctly assumed it was an ichneumon wasp. Many species in the subfamily Ichneumoninae overwinter as adults, sequestering themselves under bark, deep inside rotten logs, and other protected situations. Unfortunately, I didn’t get around to imaging this specimen (below) until after it had expired, but in my defense it is very difficult to differentiate a wasp in torpor (a state of greatly reduced metabolism) from a deceased one.

Social wasps like yellowjackets and paper wasps also overwinter as adults, though it is almost exclusively females that do so. So, I was not completely surprised to find Western Paper Wasps, Mischocyttarus flavitarsis sipping water from melting snow in a narrow arroyo in Red Rock Canyon Open Space on March 5. The high temperature on that day was 68°F.

Any female paper wasp has the potential to be the “foundress” of a new colony, so most of the females survive the winter. Only yellowjacket queens are capable of reproducing, so you will find no workers until summer. I would expect to see queens of some species out by the end of March in most places, but here at higher elevations they seem to wait much longer to emerge. Can’t blame them, as blizzards in April are not uncommon along the Front Range.

One wasp that really did surprise me was another specimen I encountered in that narrow dry arroyo. My initial observation led me to think it was a spider wasp (family Pompilidae), but I was able to get fairly close to it and get some respectable images. Turns out it was a wasp in the family Crabronidae, tribe Larrini. Members of this tribe prey mostly on crickets or grasshoppers. Considering that there are indeed grasshoppers out already, too, I guess I shouldn’t be surprised.

I’m still awaiting help to identify this wasp more specifically, but my guess is that it is probably in the genus Liris. Watch this space for updates in the comments, but don’t put your life on hold. These things take time.

Oh, I almost forgot! Just yesterday, a warm and windy 69°F day, I encountered yet another wasp on the Rock Island Trail near the intersection of Constitution Avenue and Academy Boulevard. Yes, this is pretty urban territory, paralleling an old railroad bed. What should come scurrying across the concrete path but a velvet ant (family Mutillidae). Female velvet ants are wingless wasps that, as larvae, are parasitic on other insects. They are often found digging open the burrows of other solitary wasps.

My friend Justin Schmidt thinks the assumption that velvet ants don't survive the winter may be incorrect. He is currently conducting catch-and-release experiments to see if he can find the same females in autumn and the following spring. The specimen I found is clearly encrusted with soil, suggesting she recently emerged from underground. Whether she emerged from a pupa or a hibernaculum is open to speculation.

The weather here is supposed to take a turn for the colder over the next few days, but bounce right back up into the low 60s early next week. I’ll be interested to see if the insect and spider populations skip a beat, but I doubt they will. One has to appreciate the endurance and resilience of insects, if nothing else about “bugs” is admirable.

Sunday, March 4, 2012

One thing about spiders: You don’t have to stray far from your home to find them. There is perhaps no better example of this than the Common House Spider, Parasteatoda tepidariorum. This species is so inextricably tied to human habitations that it is seldom found “in the wild.” It also owes most of its cosmopolitan geographic distribution to our global commerce in plants and other products.

Indeed, it is suspected that while the Common House Spider was first described from specimens collected in Germany, the species probably has its origins in South America where its closest allies reside (Edwards, 2001).

The species was initially assigned the name Theridion tepidariorum by Karl Ludwig Koch in 1841, but U.S. scientist A. F. Archer transferred it into his newly created genus Parasteatoda in 1946. Herbert W. Levi, a Harvard University arachnologist, then placed it in the genus Achaearanea in 1955. The current placement is back in Parasteatoda, where it is one of two species in that genus in North America, 46 species total in the world (Howe, 2012). Depending on the reference you consult, tepidariorum could be in either Parasteatoda or Achaearanea.

The pinball path of scientific nomenclature is almost matched by the number of aliases the species has in the English language: Common House Spider; American House Spider; Domestic Spider; Common Gray House Spider (in Myanmar and Pakistan).

The Common House Spider is a member of the family Theridiidae, collectively known as “cobweb weavers” or “comb-footed spiders.” Most possess a series of barbed spines on the last segment of the fourth leg. The spines help to “comb” silk from the spinnerets. The webs are large, three-dimensional structures that seem haphazard and tangled. Abandoned webs collect dust and appear as the classic “cobwebs” of scary movies.

The webs are very effective traps, however, and while flying insects can be intercepted by the irregular network of threads in the body of the web, the lines that anchor the web to the ground, or lowermost substrate, are the real traplines. Studded with sticky blobs of liquid silk, they adhere to passing ground-dwelling insects, other spiders, or even small vertebrates, holding them fast. The spider then hoists its victim into the body of the web where the spider swaths it in additional silk and renders the prey immobile. A bite is then administered and the venom acts to both paralyze or kill the prey and begin the digestive process from the inside out.

Parasteatoda tepidariorum is not considered to be dangerously venomous to people or pets, but it is frequently misidentified as the Brown Widow. Both spiders are in the family Theridiidae, build similar webs, are roughly the same size, and very similar in coloration. Indeed, I have found both species living virtually side-by-side in Redondo Beach, California. Note that the Brown Widow has a red or orange hourglass marking on the underside of the abdomen. The Common House Spider lacks this distinguishing feature.

Mature females of P. tepidariorum measure 5-8 millimeters in body length. Males average 4 millimeters. Males may share the webs of females as shown in the image below. The male is the slightly smaller, darker individual on the right. Females can live more than a year, and many individuals may occupy a relatively small area, their webs nearly contiguous. That does not mean they are peaceable, however. One that strays into its neighbor’s web may end up as dinner.

Mated females produce numerous egg sacs from late spring through late summer. The tan, papery, pear-shaped sacs may contain from 100 to more than 600 eggs each. They are familiar objects in the web, and easily identify the species.

Look for the webs of this spider in a variety of places: Under the eaves of buildings, in rock retaining walls, window wells, and tree holes. I recall finding a population of about six specimens thriving between panes in a storm window in western Massachusetts. There they fed on stray insects like the unfortunate Multicolored Asian Lady Beetle wrapped up in the image below.

I will bet you can find your own Common House Spiders today. Go take a walk around your home and see for yourself.

Friday, March 2, 2012

Walking the dog the other day (February 26, 2012), I happened upon a small caterpillar slowly crossing the sidewalk in my Colorado Springs neighborhood. It was not a cold day, but not that warm, either. The high for the day was 46 Fahrenheit. Oh, they are out today, too (current temp 49 F at 3:50 PM). Looking more closely, I discovered there were dozens of other caterpillars, all roaming seemingly aimlessly.

The stretch of sidewalk passed along the edge of a large, open field, so that offered some clues as to what the caterpillars might be. I suspected they were “cutworms” of some kind because I knew that these owlet moths (family Noctuidae) overwinter as larvae. What surprised me was that the caterpillars were clearly not mature. They were of varying sizes, but still not big enough to be on the verge of pupating.

A little bit of internet digging (“Googling”), quickly produced the most obvious suspect: the Army Cutworm, Euxoa auxiliaries. I also recognized the adult moth as something I had seen under the eave of my apartment building last October (see image below). This common “miller” moth of the western U.S. is an overwhelmingly abundant, but its life cycle is quite unique.

Colorado Springs is very much a military town, so it seems appropriate that the “Army Cutworm” is so common here. Fortunately, the roving bands of caterpillars are not armed with anything more menacing than their tiny mandibles. Not that they cannot do widespread damage anyway. They don’t call them “cutworms” for nothing. The young caterpillars chew through the stems of young, tender plants. They can also eat slow-growing plants right down to the soil. Generalist feeders, the larvae find nearly any vegetation fair game. This species is a notorious pest of virtually every field crop from alfalfa (below) and wheat to barley, oats, potato, and sugarbeets. Cereal grasses are especially vulnerable, but damage is often spotty in a given field. They seem to prefer broad-leaved weeds otherwise, nibbling on the edges of leaves or chewing holes right through them.

Ironically, while the caterpillars surface and stroll on sunny winter days, they feed mostly at night and on overcast days in the fall and spring. When disturbed they coil into a tight “C” shape until danger passes.

Thankfully, the Army Cutworm is not without its enemies. Chief among them are parasitic wasps. Research has shown that the braconid wasps Meteorus leviventris, and Apanteles griffin are among the parasites of caterpillars in Oklahoma alfalfa fields(Soteres, et al., 1984).

Many of the adult moths, which emerge in late spring and early summer, escape the scorching midsummer heat by migrating to high elevations. There in the mountains they aestivate, gathering by the thousands under boulders in rockslides, or even inside mountain cabins. They do venture out at night to sip flower nectar. Amazingly, they are a critical portion in the diet of Grizzly Bears in parts of Montana and Wyoming, at times when other food is scarce. The insects are loaded with fat and protein and the bears merely turn over rocks and lick them off.

The moths are capable of incredible endurance; and they are not completely without defense. Laboratory experiments involving tethered moths fed with sugar water showed many individuals capable of flying more than 50 miles at a time. One flew for 23 hours at a nearly constant speed of 5.8 miles per hour, achieving the equivalent of 133 miles. They can hear approaching bats with the aid of a tympanic organ in the thorax, taking appropriate evasive action to avoid predation by these flying mammals. Resting moths, when disturbed, spray a liquid substance from the rectum that probably startles a potential predator, allowing the moth to take flight (Eisner & Eisner, 1992).

Moths that survive the bears and other predators return to the lowland plains to reproduce, females laying eggs in late summer and early autumn. Eggs are deposited on bare soil, especially in cultivated or overgrazed conditions. Hatching of the eggs is triggered by rains.

The Army Cutworm ranges from the Northwest Territories and Alberta south through Washington, Oregon, and Montana to Mexico, east to Minnesota, Nebraska, and Oklahoma. Scattered records include northern Michigan, Indiana, Missouri, Texas, and Florida. Their abundance can vary greatly from year to year depending mostly on weather (Cranshaw, 2011).

I am looking forward to seeing whether my neighborhood crop of caterpillars will translate into a bumper year for adult moths this spring. I would like to see a diversity of species at my porch light, however.